1. Field of the Invention
The invention relates generally to wireless communication and more particularly to Bluetooth wireless communication.
2. Background
Consumers are increasingly demanding long battery life and more consistent connections for wireless communication devices, including short range wireless communication devices. The Bluetooth wireless communication standard, as defined in the IEEE Std 802.15, defines a short range wireless communication system (also known as a wireless personal area network (WPAN)) for use on consumer electronic devices. See IEEE Std 802.15, The Institute of Electrical and Electronics Engineers, Inc., New York, N.Y., 1999 (Reaff 2003).
There are many Bluetooth applications. One example is a cellular telephone having Bluetooth connections to a wireless (Bluetooth) headset. That is, a cellular telephone, in addition to having a cellular transceiver (e.g., U.S. personal communication system (PCS) transceiver or a global system for mobile communication (GSM) transceiver), would have a Bluetooth transceiver for communicating with a headset. The headset also has a Bluetooth transceiver. The headset additionally has a speaker and a microphone for transmitting audio information (typically voice) to and from the user. With such a Bluetooth cellular telephone and headset, the user does not have to use a loudspeaker or hold the cellular telephone close to the user's ear and mouth to talk and listen. Essentially, this is a convenient way of carrying on a “hands free” conversation.
One problem with such an arrangement is that the cellular telephone and headset consume power while searching in Bluetooth, as will be described more fully below. This is especially problematic in portable applications with limited portable power supplies, such as, for example, as described above, in cellular telephones and wireless headsets.
Another example of a Bluetooth application is a Bluetooth connection between a Bluetooth enabled cellular telephone and a Bluetooth enabled automobile. For example, a cellular telephone might download map data, such as, for example, a map, over the cellular communication network for use with the automobile navigation system. The map data may be transferred from the cellular telephone to the automobile via a Bluetooth communication.
Searching in Bluetooth consumes power. Searching can be defined as checking for the presence of another Bluetooth device or for a Bluetooth command from another device. For example, a Bluetooth module in any of the following states or modes is considered searching: page state, page scan state, inquiry state, inquiry scan state, sniff mode, hold mode and park state. See IEEE Std 802.15, Volume 2, Part B, Section 8, pp. 133-188.
Bluetooth communication systems are made up of peer to peer communications. That is, there is no base station or central network. In a Bluetooth peer to peer connection, one of the peers, known as the master Bluetooth device, or simply as the master, controls the communication. The other peer, known as the slave Bluetooth device, or simply as the slave, is controlled by the master. One master can control up to seven slaves in the present Bluetooth standard. A grouping of a master and one or more connected slaves is called a piconet. Piconets can be connected together to form a scatternet. The arrangements of piconets and scatternets will not be described further here.
In page state, a Bluetooth module transmits a Bluetooth signal attempting to connect to another particular Bluetooth device. A Bluetooth page includes the address of the particular device and asks that particular device to connect. For example, in page mode, a Bluetooth enabled cellular telephone might page the headset to establish a connection between the headset and the cellular telephone. The paging device typically becomes the master.
In page scan state, a Bluetooth module turns its receiver on and tunes its receiver to receive a Bluetooth page signal. This is also known as listening for a page. The page scanning device typically becomes the slave.
In inquiry state, a Bluetooth module transmits a Bluetooth signal asking any Bluetooth enabled devices that receives the signal to respond and give its address, so that a Bluetooth connection can be established. For example a Bluetooth enabled cellular telephone might inquire whether a Bluetooth enabled wireless headset is within range of the Bluetooth enabled cellular telephone.
In inquiry scan state a Bluetooth module turns its receiver on and tunes its receiver to receive a Bluetooth inquiry signal. This is also known as listening for an inquiry.
Sniff mode is a Bluetooth mode in which a slave Bluetooth device is made to turn its receiver off except at regular intervals. The slave device in sniff mode can save power and resources this way. However, at the regular intervals, the slave Bluetooth device turns its receiver on and listens for a signal from the master Bluetooth device. Commonly, when in sniff mode, a slave device may turn its receiver on repeatedly without returning to active communication with the master Bluetooth device.
Hold mode is a Bluetooth mode in which a slave Bluetooth device is made to turn its receiver off for a predetermined time period. The slave device in hold mode can save power and resources this way, similar to sniff mode. However, at the end of the predetermined time period, the slave Bluetooth device turns its receiver and transmitter on and returns to the active mode.
In park state, a Bluetooth module of a slave Bluetooth device is made to turn its receiver off except at regular intervals. The master Bluetooth device sends a beacon signal to the slave in the park state, to help the slave maintain the connection with the master Bluetooth device. Also, if the master Bluetooth device wants the slave Bluetooth device to return to the active mode, the master Bluetooth device will send an indicator signal as part of the beacon signal to the slave Bluetooth device telling the slave Bluetooth device to return to the active mode.
The park state is similar to sniff mode in the sense that a device in either park state or sniff mode keeps its receiver off except at regular intervals. There are other differences and similarities which will not be described here more fully. However, at the regular intervals, the slave Bluetooth device turns its receiver on and listens to the beacon signal from the master Bluetooth device. Commonly, when in the park state, a slave device may turn its receiver on repeatedly and listen to the beacon signal without returning to an active connection with the master Bluetooth device.
Accordingly, searching consumes considerable power or Bluetooth network resources or both. Further, Bluetooth page signals, inquiry signals and beacon signals can cause interference with other signals, including other Bluetooth signals and other communication system signals, such as, for example, wireless local area network (WLAN) signals, such as signals conforming to the IEEE Std 802.11b or IEEE Std 802.11g, (hereinafter, collectively “802.11”). See IEEE Std 802.11b and IEEE Std 802.11g, The Institute of Electrical and Electronics Engineers, Inc., New York, N.Y., 1999 (Reaff 2003). Both Bluetooth and 802.11 signals operate at a frequency of approximately 2.4 GHz. This makes it difficult, if not impossible, for Bluetooth and 802.11 communications to occur simultaneously in the same location.